Tesla U.S. Pat. No. 382,280 disclosed a ring built up of thin insulated annular iron plates and wound with poly-phase distributions forming an early rotating field stator for generator/motor use. Field utility was limited to the cylindrical window of the stator. Tomsk Poly Eltin In 09.06.86-SU-099729patent disclosed a device utilizing the cited Tesla stator for detecting flaws in long cylindrical objects. Eddy current induction was limited to the toroid window location.
Copending Logue patent Ser. No. 09/138,750 filed Aug. 24, 1998 disclosed a new use for the cited Tesla stator wherein the rotating hemispherical flux fringing from the plane of the toroidal stator was utilized for inducing eddy currents.
The objectives of the invention is utilization of all the known axes of permeability generated within a single toroid core for providing both driving and pick-up fields. A majority of these axes are utilized reciprocally for extending eddy current generation/detection. Also a majority of these axes are orthogonal to each other providing integral flux circuits and inherent nulling. A torus is simply a toroid with approximately 1/9 of the cross-section removed. Further, the poloidal flux circuit in a torus rotates around an axis which is in a horizonal plane.
Logue U.S. Pat. No. 5,793,204 "Method for Generating a Rotating Elliptical Sensing Pattern" introduced dynamic driving flux modulation as a means for increasing spatial resolution. To further this objective, this disclosure teaches a dynamic poloidal axis modulation to generate an orbital motion to the sensing pattern. Eccentricity is vectorially added to the sine-cosine excited rotating induction vector.
Dual rotating driving cores were introduced in Logue U.S. Pat. No. 5,754,043 coupled to concentric pick-up cores and coils. Separate poly-phase excitation generators controlled individual angular velocity. In a further version of the invention, a plurality of toroids concentrically interposed with pick-up coils on different radii provides a similar eddy current patterns.
An axis of permeability is defined in this disclosure as a cross-section of magnetic material conducting a dipole of magnetic force. This cross-section may take the form of a cylinder (z-axis), a circle (toroidal-axis), torus (poloidalaxis) or diameter-wise (x-y axes).